<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var s = 123 + "abc";
console.log(s.toUpperCase());
console.log(typeof s);
// 对象类型的字符串  引用类型的字符串
var s1 = new String(123);
console.log(typeof s1);
console.log(s1);

console.log("abc你好".length);
</script>
</body>
</html>